The present invention relates to a new method for predicting the nucleation and growth of graphite crystals during the solidification of cast irons.
WO-A1-86/01755 relates to such a method. A sample from a bath of molten iron is permitted to solidify during 0.5 to 10 minutes. The temperature is recorded simultaneously by two temperature responsive means, one of which is placed in the center of the sample and the other in the immediate vicinity of the vessel wall. The number and shape of the graphite particles which constitute the graphite phase is assessed in relation to known reference values by aid of recorded values of supercooling at the vessel wall, the recalescence at the vessel wall, the difference between the temperature at the vessel wall and at the center of the vessel and the maximum slope of the temperature time curve during the period of constant eutectic growth temperature at the center. The method can be used for calculating the amounts of inoculants and graphite structure modifiers that have to be added or removed in order to obtain a cast iron comprising a desired form of cast iron, such as flaky graphite iron, compacted graphite iron (CGI) and spheroidal graphite iron (SGI).
The method according to WO-A1-86/01755 produces excellent results, but it also has some drawbacks. The amount of time required for the determination, up to 10 minutes may be rather high, and the measurement per se is also rather complicated. Hence, there is a need for a quick, simple and reliable method for predicting the nucleation and growth of graphite crystals during the solidification of cast irons.